Hey everyone, first post here.

I'm having an issue with the heat in my 94 Jimmy (with AC). When I have the temperature control anywhere from full cold to about halfway, I get air blowing out of the vents. The dash vents, floor vents, and defrost vents, everything works fine. If the temperature control is anywhere from halfway up to full heat, I don't get any air from the vents. The blower motor runs normally, but no air comes out. I can feel heat coming from under the dashboard somewhere, but not from where it should be. I'm guessing that it has something to do with the blend door. If I slide the temperature control up and down real fast I can hear the door flapping in the dash, so I know that it at least works somewhat.

If anyone has any ideas, please help me out! Thanks for any info, Ian.

 

Take a look at these two links. When you read the first one, it will seem as if it doesn't address your problem at all. But when you read the second link it will make more sense where the connection comes in. The fact that your A/C blend seems to be fine has me thrown some. If it wasn't for that, I'd say you definitely have a vacuum problem. But maybe there is fluid behind the switch that is only causing problems for the heat. Read the links in order for a complete understanding.

GMC Sonoma & Chevy S-10 Transfer Case Vacuum Switch

GMC Sonoma & Chevy S-10 Transfer Case Vacuum Switch

 

Sorry it took so long to reply (I kinda forgot I asked this question), thanks for the info though. I haven't really looked into it too far, since it's been cold out and I don't feel like screwing with it. I still get heat, so I'll probably just wait until the spring when I can drive my car and bike to start tearing into it.